Project summary The mechanisms by which cigarette smoke (CS) activates the complement cascade to cause lung sterile inflammation and COPD progression are not completely understood. Considering the critical role of complement in pathogen-induced inflammation, selective inhibition of the mannose-binding lectin (MBL) complement pathway may result in decreased CS-induced inflammation and emphysema-like airspace enlargement without an indiscriminate inhibition of complement's response to pathogens. In Aim 1 we propose to investigate a novel mechanism of CS-induced lung injury; focusing on whether mannose-binding lectin associated serine protease-2 (MASP-2), the central protease in the MBL pathway, is necessary to induce inflammation and emphysema during CS exposure. In Aim 2 we will investigate whether alpha-1 antitrypsin, a major serine protease inhibitor, binds and inhibits MASP-2. My proposal addresses the clinically relevant question whether selective targeting of complement cascade via MASP-2 inhibition ameliorates lung inflammation and emphysema development in relevant murine models of CS exposure. Our animal studies are complemented by measurements of MASP-2 levels and activity in samples from active smokers with and without COPD. The design and implementation of the proposed coursework and experiments will assist me in gaining expertise in complement biology, enzymology, and perfect my skills in lung stereology. I will train in new techniques, such as miscroscale thermophoresis, isothermal titration calorimetry, and fluorescence resonance energy transfer, FRET - fluorescence lifetime imaging microscopy, FLIM to study alpha-1 antitrypsin binding to MASP-2. These skills and the new research focus on the role of complement system in CS-induced sterile inflammation will allow me to become an independent investigator in a different area of research than my mentor, Dr. Petrache. My committee members and collaborators are strategically positioned to assist me in completing this proposal. National Jewish Health environment, the extraordinary expertise of the mentoring team, and the track record of fruitful collaborations between Dr. Petrache and members of the committee, will ensure a multifaceted and nurturing setting to facilitate my transition to independence. Completion of this project will provide compelling experimental evidences that MASP-2 inhibition using protease inhibitors ameliorates inflammation and lung injury in murine models of emphysema and it can be harnessed as next generation therapeutics in human COPD disease.